This invention relates to a hollow blow-molded bottle-shaped container of biaxially oriented polyethylene terephthalate resin and a method of molding a hollow blow-molded bottle-shaped container of a biaxially oriented polyethylene terephthalate resin having a crystallized outer peripheral portion at the neck portion except the boundary between the neck portion and the body portion and non-crystallized inner peripheral portion thereat.
A blow-molded bottle-shaped container of a biaxially oriented polyethylene terephthalate resin, hereinafter referred to as "a PET" has a wide range of applications because of its excellent physical properties and characteristics.
Some of the excellent physical properties of a bottle-shaped container made of PET can be performed after the bottle-shaped container has been biaxially oriented and blow-molded. The bottle-shaped container of the PET has heretofore been produced due to the physical properties of the PET by the steps of injection-molding a piece or parison as a primary or prefabricated molded piece and then biaxially orienting the primary piece or parison by the so-called injection blow-molding method. Thus, the neck portion of the bottle-shaped container used as a mounting portion for the blowing mold has not entirely been oriented but been molded from the primary piece or parison to the hollow blow-molded bottle-shaped container. In this manner, the shoulder portion continued to the neck portion of the bottle-shaped container has not thus been sufficiently oriented in the course of the injection blow-molding method but has been blow-molded to the final bottle shape. Accordingly, the neck portion and the shoulder portion of the bottle-shaped container do not exhibit the excellent physical properties of the PET prepared by being subjected to the biaxially blow-molded method.
The drawbacks and disadvantages of the bottle-shaped container of the final shape thus blow-molded at the neck portion and shoulder portions which have not been subjected to or sufficiently subjected to orientation are, for example, a crazing which occurs due to the impregnation of alcohol, various deformations and strains including elongation due to lack of sufficient hardness of the bottle-shaped container, and a low thermal resistance due to the occurrence of thermal deformation when the bottle is filled with hot liquid for the purpose of sterilization. More concretely, the neck portion and the shoulder portion of the conventional bottle-shaped container thus blow-molded have such drawbacks and disadvantages that, when high internal pressure is applied to the bottle-shaped container such as in the case that carbonated drink mixed with fruit juice is filled by a hot charging process, the shoulder portion molded without being subjected to sufficient orientation is axially elongated and deformed by the internal pressure.